I. Field of the Invention
The present invention relates in general to a furnace in which chemical or physical reactions occur, and in particular to a two chamber reaction furnace wherein the chambers are disposed substantially vertically in relation to each other and the temperature of each chamber thereof can be individually controlled, with the chambers being separated from each other by a vapor-permeable partition to thereby permit interaction between reactants situated in different chambers. Also included is methodology for the interaction of reactants.
II. Description of the Prior Art
In certain chemical and physical reactions between one or more reactants, it is not unusual for reactants to require two or more different temperatures, all above ambient, for steps of a reaction to proceed. When this is the case, current single-chamber, and therefore single-temperature, furnaces require multi-step procedures to accomplish complete reactions. Such multi-step procedures can include heating a first reactant at a given temperature for an appropriate time period in a furnace, and thereafter either increasing or decreasing the furnace temperature before adding a second reactant to the furnace for a second period of time. As is apparent, such a multi-step process is both inconvenient, time-consuming, and energy inefficient while additionally requiring invasion of the furnace chamber when reactants are incompletely reacted.
Current two-zone furnaces having a first temperature zone and a second temperature zone in horizontal relationship to each other permit vaporization of a material in one zone and vapor travel to the second zone for subsequent deposition thereof. However, one major drawback of horizontal zones is that vapor deposition is not uniform, but instead a gradient of deposition quantity occurs as the vapor travels horizontally through the second temperature zone.
Exemplification of a process wherein reactants thereof require different activation temperatures in order to yield the required end product is found in the manufacture of thallium-barium-calcium-copper oxide (TBCCO) substrates having superconducting properties. In particular, a TBCCO substrate is first annealed at temperatures of about 800.degree. to 900.degree. C., at which temperature thallium is highly volatile and can be lost from the substrate. Accordingly, an external source of thallium is usually needed to compensate for any thallium loss. In a single-chamber, fixed temperature furnace, this external source is usually vaporized thallium derived from a thallium source identical to the composition of the end-product to be produced. The thallium source is heated to a temperature between about 700.degree. and 800.degree. C., thus about 100.degree. less than the annealing temperature. In a single-chamber furnace, the initial TBCCO reactant is therefore annealed first at the higher temperature. Thereafter, at the lower temperature, the initial TBCCO reactant is exposed to thallium vapor which is normally combined with an oxygen background pressure and flow. Simultaneous annealing and thallium replacement thus cannot occur in a single-chamber furnace to produce the final TBCCO substrate end-product. Employment of a two-zone horizontal furnace permits simultaneous vaporization and deposition, but, as earlier noted, creates a deposition gradient and resultant non-uniformity of desired end-product.
In view of the above, it is evident that a need is present for a two-chamber furnace where reactants therein can simultaneously react uniformly to completion when different temperature values are required for respective reactants. Therefore, a primary object of the present invention is to provide a two-chamber reaction furnace wherein the chambers are situated substantially vertically in relation to each other and wherein the temperature of each chamber can be individually controlled.
Another object of the present invention is to provide a vertical two chamber furnace wherein the chambers are separated from each other by a vapor-permeable partition to thereby permit interaction between reactants situated in different chambers and at different temperatures.
Yet another object of the present invention is to provide methodology for producing a product wherein a first reactant thereof requires a first temperature while a second reactant thereof whose vapor is to be deposited on the first reactant is so vaporized simultaneously at a second temperature.
These and other objects of the present invention will become apparent throughout the description of the invention which now follows.